The Stabilizing System of the Spine. Part II. Neutral Zone and Instability Hypothesis

Panjabi, Manohar M.

doi:10.1097/00002517-199212000-00002

Cited by 1,301 publications

(767 citation statements)

References 0 publications

Supporting

Mentioning

688

Contrasting

Unclassified

Order By: Relevance

“…The reactive force measured for the paired BAK cage was half that obtained from the strain gauge transducer, since the setup applied a 'pull-out' force to both cylinders of the construct. Neutral zone (NZ), and range of motion (ROM) were extracted from the load-displacement curves [31,50] of each loading direction for both intact and instrumented testing conditions. The mean NZ and ROM obtained for each instrumented condition of the groups was normalized to the respective mean intact values.…”

Section: Measurement Methodsmentioning

confidence: 99%

“…The NZ concept (also called laxity), introduced by Panjabi [31], is the region of physiologic intervertebral motion where the passive osteoligamentous restraints (ligaments, intervertebral disc or endplates) of a functional spinal unit (FSU) do not provide resistance to motion when loads are applied in one particular direction. Increases in NZ have been considered as indicative of injury to osteoligamentous tissue [8,28,29].…”

Section: Cage Design Characteristicsmentioning

confidence: 99%

See 1 more Smart Citation

Biomechanical stability of five stand-alone anterior lumbar interbody fusion constructs

Tsantrizos¹,

Andreou²,

Aebi³

et al. 2000

European Spine Journal

View full text Add to dashboard Cite

IntroductionInterbody fusion is preferred over postero-lateral fusion because it warrants a stronger biomechanical construct [12] and higher fusion rate [11]. It favors load transmission via the anterior column, full restoration of disc height and lordosis, annular fiber tensioning and least demands of bone graft volume [12]. A successful interbody construct provides adequate axial support to resist graft subsidence or collapse and reduces the post-operative segmental mobility to permit graft incorporation [30]. As such, the axial compressive strength and relative three-dimensional stability of an interbody construct are biomechanical measures describing the likelihood of a successful bone fusion [5].Anterior lumbar interbody fusion (ALIF) and posterior lumbar interbody fusion (PLIF) are two accepted approaches of grafted interbody fusion, the latter often combined with pedicle instrumentation [11]. The ALIF proceAbstract Anterior lumbar interbody fusion (ALIF) cages are expected to reduce segmental mobility. Current ALIF cages have different designs, suggesting differences in initial stability. The objective of this study was to compare the effect of different stand-alone ALIF cage constructs and cage-related features on initial segmental stability. Human multisegmental specimens were tested intact and with an instrumented L3/4 disc level. Five different ALIF cages (I/F, BAK, TIS, SynCage, and ScrewCage) were tested non-destructively in axial rotation, flexion/extension and lateral bending. A cage 'pull-out' concluded testing. Changes in neutral zone (NZ) and range of motion (ROM) were analyzed. Cage-related measurements normalized to vertebral dimensions were used to predict NZ and ROM. No cage construct managed to reduce NZ. The BAK and TIS cages had the largest NZ increase in flexion/extension and lateral bending, respectively. Cages did reduce ROM in all loading directions. The TIS cage was the least effective in reducing the ROM in lateral bending. Cages with sharp teeth had higher 'pull-out' forces. Antero-posterior and mediolateral cage dimensions, cage height and wedge angle were found to influence initial stability. The performance of stand-alone ALIF cage constructs generally increased the NZ in any loading direction, suggesting potential directions of initial segmental instability that may lead to permanent deformity. Differences between cages in flexion/extension and lateral bending NZ are attributed to the severity of geometrical cage-endplate surface mismatch. Stand-alone cage constructs reduced ROM effectively, but the residual ROM present indicates the presence of micromotion at the cage-endplate interface.

show abstract

Section: Measurement Methodsmentioning

confidence: 99%

Section: Cage Design Characteristicsmentioning

confidence: 99%

Biomechanical stability of five stand-alone anterior lumbar interbody fusion constructs

Tsantrizos¹,

Andreou²,

Aebi³

et al. 2000

European Spine Journal

View full text Add to dashboard Cite

show abstract

“…Data were recorded on the third cycle. From the load-deformation curves, ROM and NZ [17] were determined for the angles α, β, γ around the x, y, z axes between L1 and L3, for comparison with the initial identically performed biomechanical study [3].…”

Section: Biomechanical Testingmentioning

confidence: 99%

Vertebral body replacement with a bioglass-polyurethane composite in spine metastases - clinical, radiological and biomechanical results

Schulte¹,

Schultheiß²,

Hartwig³

et al. 2000

European Spine Journal

View full text Add to dashboard Cite

IntroductionSince advances in tumour treatment have improved the prognosis of cancer patients, the incidence of clinically apparent metastatic disease has increased [8]. Carcinomas of the breast, prostate, lung, thyroid gland and kidney account for 80% of all osseous metastatic manifestations [5]. The highest incidence of skeletal secondaries is observed in the spine, reported in one post-mortem study to be 36% [24]. Spinal metastases are primarily located in the vertebral body and in the peridural space; dorsal localisation is a rare finding [8]. Stability of the spine is impaired once the dorsal cortex of the vertebral body or the roots of the vertebral arch show signs of destruction. Local tumour progression may cause vertebral body collapse, deteriorating stability, pain and neurological symptoms. Spinal fractures may result in a kyphotic deformity Abstract Metastatic spine lesions frequently require corpectomy in order to achieve decompression of the spinal cord and restoration of spinal stability. A variety of systems have been developed for vertebral body replacement. In patients with prolonged life expectancy due to an improvement of both systemic and local therapy, treatment results can be impaired by a loosening at the implant-bone interface or mechanical failure. Furthermore, early detection of a metastatic recurrence using sensitive imaging modalities like computed tomography (CT) and magnetic resonance imaging (MRI) is possible in these patients without artefact interference. The aim of our pilot study was to evaluate the clinical applicability and results of a new radiolucent system for vertebral body replacement in the lumbar spine. The system consists of bone-integrating biocompatible materials -a polyetherurethane/bioglass composite (PU-C) replacement body and an integrated plate of carbon-fibre reinforced polyetheretherketone (CF-PEEK) -and provides high primary stability with anterior instrumentation alone. In a current prospective study, five patients with metastatic lesions of the lumbar spine were treated by corpectomy and reconstruction using this new system. Good primary stability was achieved in all cases. Follow-up (median 15 months) using CT and MRI revealed progressive osseous integration of the PU-C spacer in four patients surviving more than 6 months. Results obtained from imaging methods were confirmed following autopsy by biomechanical investigation of an explanted device. From these data, it can be concluded that implantation of the new radiolucent system provides sufficient long-term stability for the requirements of selected tumour patients with improved prognosis.

show abstract

“…Stability of the lumbar spine is a complex mechanism consisting of passive (ligaments, disks, capsules and fascia) and active (musculature) components, multi-feedback loops and motor control [1,24,27,[35][36][37]41]. Panjabi [35] designated the small passive perturbations of the intervertebral joint about the neutral position within which the viscoelastic tissues were not engaged/active as the neutral zone (NZ).…”

Section: Introductionmentioning

confidence: 99%

“…Panjabi [35] designated the small passive perturbations of the intervertebral joint about the neutral position within which the viscoelastic tissues were not engaged/active as the neutral zone (NZ). Similarly, the small increases in passive displacement or tension to the intervertebral joint which did not trigger reflexive muscular activity were designated as the neuromuscular neutral zones (NNZ) [4,18,49,51,60].…”

Section: Introductionmentioning

confidence: 99%

Motor control of lumbar instability following exposure to various cyclic load magnitudes

et al. 2009

View full text Add to dashboard Cite

The motor control system may compensate for lumbar instability following cyclic work with differential response to load magnitude. In vivo felines were exposed to a cumulative 1 h of cyclic work at 0.25 Hz. One group exposed to light whereas the second to heavy load while recording lumbar displacement and multifidus EMG during work and in single test cycles over 7 h rest post-work. Significant laxity and reduced reflexive EMG activity were evident immediately post-work in both groups. EMG and laxity recovered over 7 h rest in the group exposed to light load whereas in the group exposed to heavy load, motor control compensation was triggered within 1-2 h postwork. The compensation was expressed by earlier and stronger muscular activation than in baseline. It is concluded that cyclic work is deleterious to spine stability immediately after work. Work with heavy loads elicits delayed motor control compensation whereas work with light loads leaves the spine unstable and exposed to injury for several hours. Overall, prolonged cyclic or repetitive work elicits a transient instability disorder, regardless of the load handled, exposing the individual to potential injury.

show abstract

The Stabilizing System of the Spine. Part II. Neutral Zone and Instability Hypothesis

Cited by 1,301 publications

References 0 publications

Biomechanical stability of five stand-alone anterior lumbar interbody fusion constructs

Biomechanical stability of five stand-alone anterior lumbar interbody fusion constructs

Vertebral body replacement with a bioglass-polyurethane composite in spine metastases - clinical, radiological and biomechanical results

Motor control of lumbar instability following exposure to various cyclic load magnitudes

Contact Info

Product

Resources

About